154 IMBEDDING METHODS. 



The wax may be used exactly as paraffin, chloroform being taken as the 

 solvent (MILLER and BLACKBUEN, New York Med. Eec., 1885, p. 429 ; Amer. 

 Mon. Mic. Journ., 1887, p. 164 ; Journ. Roy. Mic. Soc., 1887, p. 1048). In 

 this case the superiority claimed for it over paraffin appears to the present 

 writer doubtful. Or, it may be used in a similar way, but with alcohol as 

 the solvent (see FEANCOTTE, Bull. Soc. Beige de Mic., 1887, p. 140; Zeit.f. 

 wiss. Mik., iv, 2, 1887, p. 230 ; Journ. Roy. Mic. Soc., 1887, p. 681). In 

 this case it has the, for some objects, valuable quality of working without 

 the accompaniment of such solvents as chloroform or benzol, which undoubt- 

 edly alter certain tissues more than alcohol. But on the whole I very much 

 doubt the possibility of its rivalling paraffin for general work, and therefore 

 refer the reader to the places quoted for the details of the manner of 

 using it. 



Soap Masses. 



282. Utility of Soap Masses. Soap masses certainly have 

 many good points. The solvent is alcohol ; the mass is highly 

 transparent, very penetrating, and a good mass cuts far better 

 than even paraffin. The mass may be cut either dry or with 

 alcohol. As to the preservation of tissues, the mass is alkaline, 

 which is against it; yet some workers still prefer soap to 

 paraffin, and it has lately been recommended by so experi- 

 enced a worker as Chun, for Siphonophora (certainly as 

 delicate a class of objects as any that exist), on the ground of 

 its producing less shrinkage than paraffin. 



283. Transparent Soap (POLZAM, Morph. Jahrb., iii, 1877, 

 3tes Heft, p. 558). The following account is taken from 

 Salensky's paper on the gemmation of Salpa, /. c. 



Take good white soap (' ' gewohnliche Kernseife"), cut it 

 up into thin slices, and put them to dry in the sun for some 

 days, until they become white. The slices are then to be 

 rubbed up to a fine powder, which is mixed with spirit to 

 the consistency of porridge. Now mix the porridge with 

 alcohol and glycerin in such proportions that the whole shall 

 contain for every 10 parts by weight of the soap, 22 parts of 

 glycerin, and 35 parts of alcohol (90 per cent.). Let the whole 

 simmer until there is obtained a perfectly transparent, syrupy, 

 somewhat yellow fluid. 



The objects, previously dehydrated in alcohol, are imbedded 

 in this mass in the usual manner. 



The mass may be removed from the sections either by means 

 of water or of very dilute alcohol. 



